Recent developments in nanotechnologies have focused on developing methods for synthesizing smaller and functional nano-structures/particles which can have better uses due to unique functional characteristics associated with nano-size/structures in industries such as biomedical, Chemical, energy, electronics, etc. [O. V. Salata, Journal of Nanobiotechnology, 2004, 2, 3]. For most of these applications metal nanoparticles have been synthesized by reduction of metal salts in both polar and non-polar solvents [Y. Li, S. Liu, T. Yao, Z. Sun, Z. Jiang, Y. Huang, H. Cheng, Y. Huang, Y. Jiang, Z. Xie, G. Pan, W. Yan, S. Wei, Dalton Trans., 2012, 41.]. The uses of non-polar solvents are preferred in many applications because of its advantage in retaining the activity of reducing agents for longer time [N. Zheng, J. Fan, G. D. Stucky, J. Am. Chem. Soc., 2006, 128, 6550]. Jun et. al. [B. H. Jun, D. H. Kim, K J Lee, U.S. Pat. No. 7,867,316B2, 2011] had described a method for manufacturing metal nanoparticles in which metal precursors were dissolved in a non-polar solvent and capping molecule solution was prepared in non-polar solvent. The used methods required heating of these solutions from 60 to 120° C. for an hr to synthesize nanoparticles of <20 nm. Lee and Wan [C. L. Lee and C. C. Wan, U.S. Pat. No. 6,572,673B2, 2003] developed a process to prepare metal nanoparticles by comprising the use of reacting metal salts and reducing agents having anionic groups, sulfate or sulfonate groups. In this method NaBH4 was used as reducing agent in water with surfactants to achieve size control synthesis of metal nanoparticles. Yang et. al. [Z. Yang, H Wang, Z Xu, U.S. Pat. No. 7,850,933B2, 2010] had described a method for synthesis of nanoparticles from metal chloride solution prepared in water and it required heating at 50-140° C. McCormick et. al. [C. L. McCormick, Andrew B. Lowe, B. S. Sumerlin, U.S. Pat. No. 8,084,558 B2, 2011] were able to prepare thiol-functionalized transition metal nanoparticles and subsequently achieving surface modification with co-polymers. Oh et. al. [S. G. Oh, S. C. Yi, S. Shin, D. W. Kim, S. H. Jeong, U.S. Pat. No. 6,660,058 B1, 2003] had highlighted the use surfactant in solutions, which have intrinsic property to adsorb into the two interfaces of different phase, to prepare silver and silver alloyed nanoparticles. The methods described above, either requires using organic solvents for the synthesis or are multistep process for the synthesis of metal nanoparticles.
Reference may be made to journal, “Journal of Nanobiotechnology, 2004, 2, 3” by Salata, wherein recent developments in nanotechnologies have focused on developing methods for synthesizing smaller and functional nano-structures/particles which can have better uses due to unique functional characteristics associated with nano-size/structures in industries such as biomedical, Chemical, energy, electronics, etc.
Reference may be made to journal, Dalton Trans., 2012, 41, 11725-11730 by Li et al wherein metal nanoparticles have been synthesized by reduction of metal salts in both polar and non-polar solvents.
Reference may be made to journal, “J. Am. Chem. Soc., 2006, 128, 6550” by Zheng et al wherein the uses of non-polar solvents are preferred in many applications because of its advantage in retaining the activity of reducing agents for longer time.
Reference may be made to U.S. Pat. No. “7,867,316B2, 2011” by Jun et al wherein a method for manufacturing metal nanoparticles in which metal precursors were dissolved in a non-polar solvent and capping molecule solution was prepared in non-polar solvent. The used methods required heating of these solutions from 60 to 120° C. for an hr to synthesize nanoparticles of <20 nm.
Reference may be made to U.S. Pat. No. “6,572,673B2, 2003” by Lee and Wen wherein a process to prepare metal nanoparticles by comprising the use of reacting metal salts and reducing agents having anionic groups, sulfate or sulfonate groups. In this method NaBH4 was used as reducing agent in water with surfactants to achieve size control synthesis of metal nanoparticles.
Reference may be made to U.S. Pat. No. “7,850,933B2, 2010” by Yang et al wherein describe the method for synthesis of nanoparticles from metal chloride solution prepared in water and it required heating at 50-140° C.
Reference may be made to U.S. Pat. No. “8,08,4558 B2, 2011” by McCormick et al wherein thiol-functionalized transition metal nanoparticles was prepared and subsequently achieving surface modification with co-polymers.
Reference may be made to U.S. Pat. No. “6,660,058 B1, 2003” by Oh et al wherein describe the use of surfactant in solutions, which have intrinsic property to adsorb into the two interfaces of different phase, to prepare silver and silver alloyed nanoparticles.
In non-polar solvent methods highly monodisperse nanoparticles can be achieved, due to the controlled reduction of metal precursors by the use of reducing chemicals. This makes nonpolar solvent to be desirable in most of the methods used for synthesis of metal nanoparticles. Despite of several advantages these processes for nanoparticle synthesis require multiple steps to control the size of nanoparticles and to achieve higher stability. Secondly the use of most of non-polar solvents is not desirable for their cost effectiveness and adverse effects on the environment.
Developing methods for rapid and cost effective synthesis of metal nanoparticles in polar solvent can be desirable. However, there are not many reports and methods which specifically describe the role of reducing chemicals in these solvents in which the strong reducing power of these in water can be utilized for the reduction of metal salts. Hence there is an urgent need for developing methods for synthesis of metal nanoparticles at room temperature.